and the sun stops shining at night. In
contrast, power generated from coal
and natural gas is consistent, and able
to be ramped up and down quickly to
meet demand.
This presents a conundrum for
clean energy advocates. How do you
make renewable energy not only
cheap enough, but reliable enough, to
compete with fossil fuels?
The answer may lie in the types of
energy storage used to capture the
power generated from these renewable sources. Better batteries could
make it possible for utility companies
to leverage renewable energy sources
at scale as primary power sources,
rather than as clean backups to traditional dirty fuels.
Powering the Grid
The power grids that charge and recharge modern life are complicated
beasts, comprised of many different
companies and technologies that
make it possible to generate power,
then route that power to homes and
businesses.
These grids operate on a basic
principle: once energy is generated,
it is sent out for consumption. If it
is not being consumed immediately,
it needs to be stored in some fashion so it can be released back into
the grid when end users are ready to
consume it.
It sounds easy in theory, but it
quickly gets complicated in practice.
When businesses and homes need
power, they typically need it immediately. This means demand for grid
power can fluctuate a lot, and it can
fluctuate quickly. Power supply must
match demand as adequately as possible, on time and on budget. Failure to
meet demand sufficiently and on time
results in power failures or blackouts.
Failure to meet demand on-budget
means a power provider eventually
goes out of business.
This is where the benefits of fossil
fuels become evident. Fossil fuel-pow-
ered energy plants generate consis-
tent power, since humans, not nature,
control their fuel sources, and the
different fossil fuel power generation
technologies (such as coal, oil, and
natural gas) can be scaled up or down
to meet demand fluctuations. Despite
being dirty (basically, the fuels are
burned to heat water to turn turbines
that generate electricity, releasing car-
bon dioxide and other contaminants
into the atmosphere in the process),
they are (at the moment) reliable.
Renewable energy sources, on the
other hand, are clean and their fuel
is free and abundant. However, the
power generated by water, wind, and
solar sources must be stored somewhere after it is generated, since it is
intermittent.
The top method utilized in the
U.S. for renewable energy storage is
pumped-storage hydroelectric, which
provides 95% of grid-scale electricity storage in the country, according
to the U.S. Department of Energy.
Pumped-storage hydro utilizes multiple reservoirs to store and release
electricity in a highly efficient and
responsive manner, allowing power
grids to react quickly to fluctuations
in demand.
According to electric power holding company Duke Energy, “
Pumped-storage hydro plants store and generate energy by moving water between
two reservoirs at different elevations.”
When demand is low, “Excess energy
is used to pump water to an upper reservoir.” When there’s high demand,
the water is released from the upper
reservoir to generate power.
However, building these storage
systems requires massive time and resource investments, and the location
of these storage systems is highly dependent on geography.
This is where battery technology
comes in. On the grid, the right bat-
tery technology may be able to store
and release energy at far less cost than
pumped-storage hydro. Some battery
developments are also enabling the
transition to electric vehicles, further
reducing reliance on non-renewable
fossil fuels.
One of the main battery types currently used for energy storage is the
lithium-ion battery. Lithium-ion
batteries power the handheld tech
gadgets we use every day, including
smartphones. They also provide energy storage for electric cars, and extremely large lithium-ion batteries
are increasingly being used in power
grids to store energy from renewable
sources.
Lithium-ion batteries are inexpensive and energy-dense compared to
batteries made with other materials.
They also degrade relatively slowly,
losing just a fraction of their power after each use.
“Over the past decade, we have
seen a tremendous cost reduction of
lithium-ion battery technology, by approximately 10 times,” says William
Chueh, an assistant professor of Mate-
rials Science and Engineering at Stan-
ford University working on renewable
energy storage technologies. “This
has been responsible for the boom in
electric vehicles and for storing inter-
mittent solar and wind electricity.”
However, lithium-ion batteries
have one big problem: they still are
not priced competitively enough to be
used at scale on grids to store energy
from renewable sources.
“To realize a complete penetration
of batteries for storing intermittent
renewable electricity, the cost needs
to decrease by another order of mag-
nitude, and the scalability needs to be
greatly improved,” says Chueh.
Those developments are unlike-
ly, says Ben Schiltz, head of Energy
Storage Communications at the U.S.
Department of Energy’s Argonne Na-
tional Laboratory, which has multiple
energy storage research projects in
progress.
“Today, the industry continues to
make incremental improvements to
lithium-ion batteries. However, we
are reaching the theoretical limit of
what can be done with these batter-
ies,” Schiltz says. “Developing safe
“Incumbent
technologies
are still on a steep
cost-down curve,
which is challenging
for new technologies
to compete with,” says
Stanford University’s
William Chueh.